This invention relates to multi-channel audio origination and reproduction.
Increasing demands for realistic audio reproduction from consumers and music professionals, and the abilities of modern compression technology to store and deliver multichannel audio at bit rates that are feasible, as well as current consumer trends, show that multichannel (herein, more than two channels) sound is coming to consumer audio and the “home theater.” Numerous microphone techniques, mixing techniques, and playback formats have been suggested, but a great deal of this effort has ignored the long-established requirements that have been found necessary for good perceived sound-field reproduction. As a result, soundfield capture and reproduction remains one of the key research challenges to audio engineers.
The main goal of soundfield reproduction is to reconstruct the spatial, temporal and qualitative aspects of a particular venue as faithfully as possible when playing back in the consumer's listening room. Artisans in the field understand, however, that exact soundfield reproduction is unlikely to be achieved, and probably impossible to achieve, for basic physical reasons.
There have been numerous attempts to capture the experience of a concert hall on recordings, but these attempts seem to have been limited primarily to the idea of either co-incident miking, which discards the interaural time difference, or widely spaced miking, which provides time cues that are not of the range 0 to ±0.9 msec, and thus provide cues that are either not expected by the auditory system or constitute contradictory information. The one exception appears to be binaural miking methods, and their derivatives, which do two-channel recording and which attempt to take some account of human head shape and perception, but which create difficulties both in the matching of the “artificial head” or other recording mount, and which do not allow the listener to sample the soundfield by small head movements. (Listeners unconsciously use small head movements to sample soundfields in normal listening environments.)
In the realm of multichannel audio, current mixing methods consist of either co-incident miking (ambiphonics) or widely spaced miking (the purpose being to de-correlate the different recorded channels), neither of which provides both the amplitude and time cues that the human auditory system expects.